In an electrophotographic-type image-forming device, first an electrostatic latent image is formed on the surface of a photosensitive drum as the drum rotates. Next, toner is supplied by a developing roller to the surface of the photosensitive drum, for developing the electrostatic latent image into a toner image. Subsequently, the toner image carried on the surface of the photosensitive drum is transferred onto a sheet of paper. Through this process, the image-forming device can form images (toner images) on paper.
At this time, any charge remaining on the surface of the photosensitive drum after a toner image has been transferred onto paper can adversely affect the quality of the next electrostatic latent image (toner image) formed on the photosensitive drum. Therefore, some conventional image-forming devices have been provided with a charge-removing device for removing any residual charge from the surface of the photosensitive drum.
One charge-removing device known in the art is provided with an LED array. The LED array is disposed in opposition to the surface of the photosensitive drum and is configured of a plurality of light-emitting diodes (LEDs) aligned along the axis of the photosensitive drum. By emitting light from each LED so that the surface of the photosensitive drum is uniformly irradiated across the entire drum in the axial direction thereof, residual charge can be removed from the surface of the drum.
Another type of charge-removing device known in the art is configured of an LED lamp, and a light guide for guiding light emitted from the LED lamp onto the surface of the photosensitive drum. The light guide is formed of a transparent resin or glass and is bar-shaped. The bar-shaped light guide is positioned opposite the surface of the photosensitive drum so as to extend in the axial direction of the drum. The LED lamp is positioned opposite one endface of the light guide so that light emitted from the LED lamp enters this endface. V-shaped notches formed of recesses and protrusions are provided in the peripheral surface of the light guide for reflecting light entering the endface from the LED lamp onto the surface of the photosensitive drum. In order to prevent a decrease in the quantity of light irradiated onto the surface of the photosensitive drum as the distance from the LED lamp increases, the width and depth of the recesses and protrusions formed in the light guide are increased monotically in the direction away from the LED lamp.
Since the charge-removing device configured of an LED lamp and a light guide requires fewer LEDs than the charge-removing device configured of an LED array, the cost of the charge-removing device can be reduced.